UNSET_EXPIRY
printf("expire\t\t%s\n", (u.u_expire == NULL) ? UNSET_EXPIRY : u.u_expire);
fprintf(fp, "expire\t\t%s\n", (up->u_expire == NULL) ? UNSET_EXPIRY : up->u_expire) <= 0 ||
if (strcmp(cp, UNSET_EXPIRY) == 0) {